Unreactive monatomic gases

Cesium, atomic number 55, is the most active naturally occurring metal. Francium and radium are radioactive and do not occur in nature in appreciable amounts. Noble gases seldom bond with other elements. They are unreactive, monatomic gases. The most active nonmetal is fluorine, atomic number 9. 

Despite xenon s relatively high reactivity (which isn t really high at all) the Group 18 elements 2ire considered unreactive monatomic gases. The only other noble gas to form any compound is krypton, which can form a very unstable difluoride binary compound. Compounds of noble gases, typically that of xenon, have oxidation states of +2, +4, +6, and +8. 

For several reasons — including the complete breakdown of sample into its substituent elements in the plasma and the use of an unreactive monatomic plasma gas (argon) — background interferences in the resulting mass spectra are of little importance. Since there are no or very few background overlaps with sample ions, very precise measurements of sample ion abundances can be made, which facilitate the determination of precise isotope ratios. 

In Group 8A(I8), all of the elements have the condensed configuration [noble gas] ns np. Consistent with their filled energy levels, all of these elements are monatomic gases that are extremely unreactive. 

Helium is one of the noble gases the others are neon, argon, krypton, xenon, and radon (Family 18, or VIIIA). These gases are described as noble or inert because they only form compounds under extraordinary conditions. They are all monatomic, which means that the fundamental unit is the atom rather than the diatomic molecule found as the fundamental unit for other gaseous elements, such as H2 and CI2. Helium is used whenever a very light unreactive gas is needed, such as in toy balloons and blimps. 

The idea of the covalent bond was first suggested by the American physical chemist Gilbert Newton Lewis (1875-1946) in 1916. He pointed out that the electron configuration of the noble gases appears to be a particularly stable one. Noble-gas atoms are themselves extremely unreactive. Moreover, as pointed out in Chapter 6, a great many monatomic ions have noble-gas structures. Lewis suggested that nonmetal atoms, by sharing electrons to form an electron-pairbond, can acquire a stable noble-gas structure. Consider,... 

---